If you understand HBD, I think you have to agree that high marginal tax rates are equivalent to segregation.
Neighborhoods that are highly "diverse" have bad schools (i.e. schools filled with NAMs). If rich people (especially if "rich" means recently earned a fair amount above average) live in these neighborhoods and they’re taxed at high rates, they effectively have no choice other than moving to areas that have good schools (i.e. areas that are not diverse). If smart people are more likely to be rich, and certain groups of people are more likely to be smart, then high tax rates will result in segregation.
High marginal tax rates therefore are effectively equivalent to segregation. QED.